Double-headed piston type swash plate compressor

ABSTRACT

A double-headed piston type swash plate compressor includes a housing and a rotary shaft. The housing defines a swash plate chamber and includes a cylinder block, a front housing member coupled to a front end of the cylinder block, and a rear housing member coupled to a rear end of the cylinder block. The rotary shaft is supported by the housing. A protrusion is provided in a suction chamber of the rear housing member and protrudes toward an opening of an axial passage formed in the rotary shaft. A restrictor through which refrigerant passes when flowing from the suction chamber to the axial passage is formed between the protrusion and the rear end of the rotary shaft. The protrusion has a distal end sized such that the distal end can be inserted in the opening of the axial passage.

BACKGROUND OF THE INVENTION

The present invention relates to a double-headed piston type swash plate compressor.

A double-headed piston type swash plate compressor includes a cylinder block, a front housing member coupled to the front end of the cylinder block, and a rear housing member coupled to the rear end of the cylinder block. The cylinder block defines a swash plate chamber, and the swash plate chamber accommodates a swash plate that rotates together with a rotary shaft. To the swash plate are engaged double-headed pistons. The cylinder block defines cylinder bores, which accommodate the double-headed pistons. Each double-headed piston reciprocates in the corresponding cylinder bore in accordance with rotation of the swash plate. The double-headed piston divides the inside of the cylinder bore into a first compression chamber on the front end and a second compression chamber on the rear end. In accordance with the reciprocation of the double-headed pistons, refrigerant is drawn into the first compression chambers and the second compression chambers to be compressed, and the compressed refrigerant is discharged into a first discharge chamber formed in the front housing member and a second discharge chamber formed in the rear housing member.

Structures for drawing refrigerant into the first compression chambers and the second compression chambers include the structure employed by the compressor disclosed in, for example, Japanese Laid-Open Patent Publication No. 5-133325. The compressor of the publication includes a first suction chamber in the front housing member and a second suction chamber in the rear housing member. The cylinder block includes a suction passage that connects the swash plate chamber to the first suction chamber and a suction passage that connects the swash plate chamber to the second suction chamber. Refrigerant is introduced into the swash plate chamber, and the refrigerant that has been introduced to the swash plate chamber is supplied to the first suction chamber and the second suction chamber through the corresponding suction passage. Furthermore, when the pressure in each cylinder bore is reduced and a suction reed valve opens, the refrigerant is drawn from the first suction chamber into the associated first compression chamber or from the second suction chamber into the associated second compression chamber.

In Japanese Laid-Open Patent Publication No. 5-133325, the refrigerant presses open the suction reed valves to be drawn from the first suction chamber and the second suction chamber into the first compression chambers and the second compression chambers. Thus, suction loss of refrigerant occurs when the refrigerant presses open the suction reed valves. This consequently reduces the compression efficiency. Furthermore, the refrigerant introduced into the swash plate chamber is heated by the heat generated in sliding parts such as the swash plate and the rotary shaft.

The compressor disclosed in, for example, Japanese Laid-Open Patent Publication No. 2004-278460 includes a suction chamber only in the rear housing member and has an axial passage formed in the rotary shaft to be connected to the suction chamber. The rotary shaft includes a first rotary valve corresponding to the first compression chambers and a second rotary valve corresponding to the second compression chambers. Each rotary valve is selectively opened and closed in accordance with rotation of the rotary shaft. This draws the refrigerant, which is introduced from the suction chamber into the axial passage, into the compression chambers through the rotary valves. The compressor of Japanese Laid-Open Patent Publication No. 2004-278460 eliminates the suction loss of the refrigerant that occurs by pressing open the suction reed valves and has favorable compression efficiency. In addition, since the refrigerant is not introduced into the swash plate chamber, the refrigerant is prevented from being heated by the heat generated in the sliding parts such as the swash plate and the rotary shaft.

However, unlike the compressor of Japanese Laid-Open Patent Publication No. 5-133325, the compressor of Japanese Laid-Open Patent Publication No. 2004-278460 does not introduce the refrigerant into a relatively large space like the swash plate chamber. Thus, suction pulsation of refrigerant tends to occur during suction strokes. The dimensional restriction of the double-headed piston type swash plate compressor restricts increase in the size of the suction chamber formed in the rear housing member like the structure in Japanese Laid-Open Patent Publication No. 2004-278460. Thus, the suction pulsation of the refrigerant is relatively great in the compressor of Japanese Laid-Open Patent Publication No. 2004-278460.

SUMMARY OF THE INVENTION

Accordingly, it is an objective of the present invention to provide a double-headed piston type swash plate compressor that has reduced suction pulsation of refrigerant.

To achieve the foregoing objective and in accordance with one aspect of the present invention, a double-headed piston type swash plate compressor is provided that includes a housing defining a swash plate chamber. The housing includes a cylinder block, a front housing member coupled to a front end of the cylinder block, and a rear housing member coupled to a rear end of the cylinder block. The compressor further includes a rotary shaft supported by the housing, a swash plate that is accommodated in the swash plate chamber and configured to rotate with the rotary shaft, a double-headed piston engaged with the swash plate, a cylinder bore that is formed in the cylinder block and accommodates the double-headed piston, a first compression chamber defined in the front end of the cylinder bore by the double-headed piston, a second compression chamber defined in the rear end of the cylinder bore by the double-headed piston, a suction chamber formed in the rear housing member, an axial passage that is formed in the rotary shaft to be connected to the suction chamber and includes an opening that opens to the suction chamber, a first rotary valve that selectively connects and disconnects the axial passage to and from the first compression chamber in accordance with rotation of the rotary shaft, and a second rotary valve that selectively connects and disconnects the axial passage to and from the second compression chamber in accordance with rotation of the rotary shaft. The rear housing member includes a protrusion provided in the suction chamber and protruding toward the opening of the axial passage. A restrictor through which refrigerant passes when flowing from the suction chamber to the axial passage is formed between the protrusion and the rear end of the rotary shaft. The protrusion has a distal end sized such that the distal end can be inserted in the opening of the axial passage.

Other aspects and advantages of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:

FIG. 1 is a cross-sectional side view illustrating a double-headed piston type swash plate compressor according to a first embodiment;

FIG. 2 is an enlarged cross-sectional view illustrating a protrusion and its surroundings in the compressor of FIG. 1;

FIG. 3 is an enlarged cross-sectional view illustrating a protrusion and its surroundings of a double-headed piston type swash plate compressor according to a second embodiment; and

FIG. 4 is an enlarged cross-sectional view illustrating a protrusion and its surroundings of a double-headed piston type swash plate compressor according to a third embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A double-headed piston type swash plate compressor 10 according to a first embodiment will now be described with reference to FIGS. 1 and 2.

As shown in FIG. 1, the double-headed piston type swash plate compressor 10 has a housing H. The housing H includes front and rear cylinder blocks 11, 12 coupled to each other, a front housing member 13 coupled to the front end of the front cylinder block 11, and a rear housing member 14 coupled to the rear end of the rear cylinder block 12. The cylinder blocks 11, 12 and the housing members 13, 14 are secured together with multiple bolts B.

The compressor 10 includes a first valve plate 15, a first valve sub-plate 16, and a first retainer plate 17 between the front housing member 13 and the front cylinder block 11. The compressor 10 further includes a second valve plate 18, a second valve sub-plate 19, and a second retainer plate 20 between the rear housing member 14 and the rear cylinder block 12. The first valve plate 15 includes multiple first discharge ports 15 a, and the second valve plate 18 includes multiple second discharge ports 18 a. The first valve sub-plate 16 includes multiple first discharge valves 16 a, and the second valve sub-plate 19 includes multiple second discharge valves 19 a. The discharge valves 16 a, 19 a selectively open and close the corresponding discharge ports 15 a, 18 a. The first retainer plate 17 includes multiple first retainers 17 a, and the second retainer plate 20 includes multiple second retainers 20 a. The retainers 17 a, 20 a regulate the opening degree of the corresponding discharge valves 16 a, 19 a.

The front housing member 13 and the first valve plate 15 define a first discharge chamber 13 a. The rear housing member 14 and the second valve plate 18 define a second discharge chamber 14 a and a suction chamber 14 b. The first discharge chamber 13 a and the second discharge chamber 14 a are connected to a non-illustrated discharge passage, and the discharge passage is connected to a non-illustrated external refrigerant circuit.

The cylinder blocks 11, 12 rotationally support a rotary shaft 21, and the rotary shaft 21 has a central axis L. The front end of the rotary shaft 21 is inserted in a shaft hole 11 a formed in the front cylinder block 11. The rear end of the rotary shaft 21 is inserted in a shaft hole 12 a formed in the rear cylinder block 12. The front end of the rotary shaft 21 is rotationally supported by the front cylinder block 11. The rear end of the rotary shaft 21 is rotationally supported by the rear cylinder block 12. The rear end of the rotary shaft 21 extends through the second valve plate 18, the second valve sub-plate 19, and the second retainer plate 20 and protrudes in the suction chamber 14 b.

Between the front housing member 13 and the rotary shaft 21 is provided a lip seal, which is a shaft seal 22. The shaft seal 22 is accommodated in an accommodation chamber 13 b formed in the front housing member 13. The first discharge chamber 13 a is provided around the accommodation chamber 13 b.

On the rotary shaft 21 is mounted a swash plate 23, which rotates with the rotary shaft 21. The swash plate 23 is accommodated in the internal space of the cylinder blocks 11, 12, that is, a swash plate chamber 24 defined in the housing H. The swash plate 23 includes an annular base 23 a around the rotary shaft 21. Between the front cylinder block 11 and the base 23 a of the swash plate 23 is provided a first thrust bearing 25. Between the rear cylinder block 12 and the base 23 a of the swash plate 23 is provided a second thrust bearing 26. The thrust bearings 25, 26 sandwich the swash plate 23 to limit the movement of the swash plate 23 along the central axis L of the rotary shaft 21.

The front cylinder block 11 includes multiple through holes 11 h (only one is shown in FIG. 1) arranged around the rotary shaft 21. The rear cylinder block 12 includes multiple through holes 12 h (only one is shown in FIG. 1) arranged around the rotary shaft 21. Pairs of one of the front through holes 11 h and an associated one of the rear through holes 12 h form cylinder bores 27. Each cylinder bore 27 accommodates a double-headed piston 28 to reciprocate in the front and rear direction. Each double-headed piston 28 is engaged with the swash plate 23 via a pair of shoes 29. The swash plate 23 rotates integrally with the rotary shaft 21. The rotation of the swash plate 23 is transmitted to each double-headed piston 28 via the associated pair of shoes 29 and reciprocates the double-headed piston 28 back and forth in the associated cylinder bore 27.

In the front section of each cylinder bore 27, the first valve plate 15 and the associated double-headed piston 28 define a first compression chamber 27 a. In the rear section of each cylinder bore 27, the second valve plate 18 and the associated double-headed piston 28 define a second compression chamber 27 b.

The inner circumferential surfaces of the shaft holes 11 a, 12 a have sealing circumferential surfaces 11 b, 12 b. The rotary shaft 21 is directly supported by the cylinder blocks 11, 12 on the sealing circumferential surfaces 11 b, 12 b. The rotary shaft 21 includes an axial passage 21 a inside the rotary shaft 21. The axial passage 21 a has an opening 211 a that opens in a rear direction of the rotary shaft 21, that is, toward the rear housing member 14. The opening 211 a opens in the suction chamber 14 b. That is, the axial passage 21 a is connected to the suction chamber 14 b via the opening 211 a.

The rotary shaft 21 includes a first introduction passage 31 at a position corresponding to the front cylinder block 11 in the axial direction. The first introduction passage 31 connects the axial passage 21 a to the outer circumference of the rotary shaft 21. The rotary shaft 21 also includes a second introduction passage 32 at a position corresponding to the rear cylinder block 12 in the axial direction. The second introduction passage 32 connects the axial passage 21 a to the outer circumference of the rotary shaft 21.

The front cylinder block 11 includes multiple first suction passages 33 (only one is shown in FIG. 1), and each first suction passage 33 connects the front section of the corresponding cylinder bore 27 to the shaft hole 11 a. Each first suction passage 33 has an opening that opens to the sealing circumferential surface 11 b to connect the first suction passage 33 to the shaft hole 11 a. The rear cylinder block 12 includes multiple second suction passages 34 (only one is shown in FIG. 1), and each second suction passage 34 connects the rear section of the corresponding cylinder bore 27 to the shaft hole 12 a. Each second suction passage 34 has an opening that opens to the sealing circumferential surface 12 b to connect the second suction passage 34 to the shaft hole 12 a.

The first introduction passage 31 is formed at a position where the first introduction passage 31 is intermittently connected to the first suction passages 33 in accordance with the rotation of the rotary shaft 21. The second introduction passage 32 is formed at a position where the second introduction passage 32 is intermittently connected to the second suction passages 34 in accordance with the rotation of the rotary shaft 21. That is, the first introduction passage 31 is arranged at the same position as the openings of the suction passages 33 in the axial direction of the rotary shaft 21, and the second introduction passage 32 is arranged at the same position as the openings of the suction passages 34 in the axial direction of the rotary shaft 21. The rotary shaft 21 includes a first rotary valve 35 at a portion surrounded by the sealing circumferential surface 11 b, and the first rotary valve 35 is formed integrally with the front portion of the rotary shaft 21. The rotary shaft 21 also includes a second rotary valve 36 at a portion surrounded by the sealing circumferential surface 12 b, and the second rotary valve 36 is formed integrally with the rear portion of the rotary shaft 21.

When the first introduction passage 31 is connected to one of the first suction passages 33 in accordance with the rotation of the rotary shaft 21, the first rotary valve 35 is in an open state that permits connection between the axial passage 21 a and the associated first compression chamber 27 a via the passages 31, 33. When the first introduction passage 31 and the first suction passage 33 are disconnected in accordance with the rotation of the rotary shaft 21, the first rotary valve 35 is in a closed state that blocks the connection between the axial passage 21 a and the first compression chamber 27 a via the passages 31, 33. Thus, the first rotary valve 35 selectively connects and disconnects the axial passage 21 a with and from the first compression chambers 27 a in accordance with the rotation of the rotary shaft 21.

When the second introduction passage 32 is connected to one of the second suction passages 34 in accordance with the rotation of the rotary shaft 21, the second rotary valve 36 is in an open state that permits connection between the axial passage 21 a and the associated second compression chamber 27 b via the passages 32, 34. When the second introduction passage 32 and the second suction passage 34 are disconnected in accordance with the rotation of the rotary shaft 21, the second rotary valve 36 is in a closed state that blocks the connection between the axial passage 21 a and the second compression chamber 27 b via the passages 32, 34. Thus, the second rotary valve 36 selectively connects and disconnects the axial passage 21 a with and from the second compression chambers 27 b in accordance with the rotation of the rotary shaft 21.

The rear housing member 14 includes an introduction port 37 connected to the suction chamber 14 b. The introduction port 37 is connected to the external refrigerant circuit and introduces the refrigerant from the external refrigerant circuit into the suction chamber 14 b. The introduction port 37 extends in a direction perpendicular to the axial direction of the rotary shaft 21, that is, in the radial direction of the rotary shaft 21.

As shown in FIG. 2, the rear housing member 14 includes, in the suction chamber 14 b, a conical protrusion 40, which protrudes toward the opening 211 a of the axial passage 21 a. The protrusion 40 is formed, through die casting, integrally with the inner wall of the rear housing member 14, which defines the suction chamber 14 b and faces the rear end of the rotary shaft 21. The protrusion 40 is tapered toward a distal end 40 e and has a diameter decreasing toward the distal end 40 e. The distal end 40 e of the protrusion 40 has a flat end face. The distal end 40 e of the protrusion 40 extends into the axial passage 21 a. Between the protrusion 40 and the rear end of the rotary shaft 21, or more specifically, between the protrusion 40 and the periphery of the opening 211 a located around the protrusion 40 is formed an annular restricting portion 41. The restricting portion 41 restricts the flow of the refrigerant flowing through the restricting portion 41. The cross-sectional area of the distal end 40 e of the protrusion 40 perpendicular to the central axis L of the rotary shaft 21 is smaller than the cross-sectional area of the opening 211 a of the axial passage 21 a, which is perpendicular to the central axis L of the rotary shaft 21. That is, the distal end 40 e of the protrusion 40 is sized such that the distal end 40 e can be inserted in the axial passage 21 a.

Operation of the first embodiment will now be described.

When refrigerant is introduced from the external refrigerant circuit to the suction chamber 14 b through the introduction port 37, the refrigerant introduced to the suction chamber 14 b collides against the protrusion 40. The refrigerant is guided along the protrusion 40 toward the axial passage 21 a and flows into the axial passage 21 a through the restrictor 41. When the first rotary valve 35 and the second rotary valve 36 are opened in accordance with the rotation of the rotary shaft 21, the refrigerant that has flowed into the axial passage 21 a is drawn into the associated first compression chamber 27 a and the associated second compression chamber 27 b. During suction of the refrigerant from the suction chamber 14 b to the first compression chamber 27 a and the second compression chamber 27 b, the refrigerant passes through the restrictor 41 so that the suction pulsation of the refrigerant is reduced.

The first embodiment achieves the following advantages.

(1) The rear housing member 14 has the protrusion 40, which protrudes toward the opening 211 a of the axial passage 21 a in the suction chamber 14 b. The restrictor 41 is formed between the protrusion 40 and the rear end of the rotary shaft 21. The structure allows the refrigerant introduced in the suction chamber 14 b to flow into the axial passage 21 a through the restrictor 41. When the first rotary valve 35 and the second rotary valve 36 are opened in accordance with the rotation of the rotary shaft 21, the refrigerant that has flowed into the axial passage 21 a is drawn into the associated first compression chamber 27 a and the associated second compression chamber 27 b. During suction of the refrigerant from the suction chamber 14 b to the first compression chamber 27 a and the second compression chamber 27 b, the refrigerant passes through the restrictor 41 so that the suction pulsation of the refrigerant is reduced.

(2) The distal end 40 e of the protrusion 40 extends into the axial passage 21 a. The structure allows the restrictor 41 to be easily formed as compared to a case where the distal end 40 e of the protrusion 40 extends to the same position as the rear end of the rotary shaft 21 in the axial direction and does not extend into the axial passage 21 a. As a result, the suction pulsation of the refrigerant is further reduced in a suitable manner.

(3) The protrusion 40 is tapered. The structure allows the refrigerant introduced into the suction chamber 14 b to be guided by the protrusion 40 toward the axial passage 21 a. Thus, the refrigerant smoothly flows from the suction chamber 14 b into the axial passage 21 a. This reduces the suction loss of the refrigerant and also reduces the suction pulsation of the refrigerant.

(4) The introduction port 37 extends in the direction perpendicular to the axial direction of the rotary shaft 21. The structure allows the refrigerant introduced from the introduction port 37 into the suction chamber 14 b to be more smoothly guided along the protrusion 40 toward the axial passage 21 a as compared to a case where the introduction port 37 extends parallel to the axial direction of the rotary shaft 21. This reduces the suction loss of the refrigerant and further reduces the suction pulsation of the refrigerant.

(5) The protrusion 40 is formed integrally with the inner wall of the rear housing member 14. The structure improves the productivity of the protrusion 40 as compared to a case where, for example, a protrusion formed as a separate member from the rear housing member 14 is attached to the rear housing member 14.

The first embodiment may be modified as follows.

Like a second embodiment shown in FIG. 3, the distal end 40 e of the protrusion 40 may be semi-spherical. The structure allows the refrigerant to smoothly flow around the distal end 40 e of the protrusion 40 and further reduces the suction loss of the refrigerant.

Like a third embodiment shown in FIG. 4, the protrusion 40 may be columnar. That is, the protrusion 40 does not need to be tapered. The protrusion 40 may be a column extending in the axial direction of the rotary shaft 21, or more specifically, the protrusion 40 may have a constant cross-sectional shape and cross-sectional area in the axial direction of the rotary shaft 21. Furthermore, the distal end 40 e of the columnar protrusion 40 may be semi-spherical as shown in FIG. 3.

The introduction port 37 may extend in a direction intersecting the axial direction of the rotary shaft 21.

The introduction port 37 may extend parallel to the axial direction of the rotary shaft 21.

The distal end 40 e of the protrusion 40 does not necessarily have to extend into the axial passage 21 a, but may extend to the same position as the rear end of the rotary shaft 21 in the axial direction. In other words, the distal end 40 e of the protrusion 40 may be located at any position where the restrictor 41 can be formed between the protrusion 40 and the rear end of the rotary shaft 21.

The protrusion 40 may be formed as a separate member from the rear housing member 14.

Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims. 

1. A double-headed piston type swash plate compressor, comprising: a housing defining a swash plate chamber, wherein the housing includes a cylinder block, a front housing member coupled to a front end of the cylinder block, and a rear housing member coupled to a rear end of the cylinder block; a rotary shaft supported by the housing; a swash plate that is accommodated in the swash plate chamber and configured to rotate with the rotary shaft; a double-headed piston engaged with the swash plate; a cylinder bore that is formed in the cylinder block and accommodates the double-headed piston; a first compression chamber defined in the front end of the cylinder bore by the double-headed piston; a second compression chamber defined in the rear end of the cylinder bore by the double-headed piston; a suction chamber formed in the rear housing member; an axial passage that is formed in the rotary shaft to be connected to the suction chamber and includes an opening that opens to the suction chamber; a first rotary valve that selectively connects and disconnects the axial passage to and from the first compression chamber in accordance with rotation of the rotary shaft; a second rotary valve that selectively connects and disconnects the axial passage to and from the second compression chamber in accordance with rotation of the rotary shaft; and a protrusion provided in the suction chamber and protruding toward the opening of the axial passage, wherein a restrictor through which refrigerant passes when flowing from the suction chamber to the axial passage is formed between the protrusion and the rear end of the rotary shaft, and the protrusion has a distal end sized such that the distal end is insertable in the opening of the axial passage.
 2. The compressor according to claim 1, wherein the distal end of the protrusion is inserted in the axial passage.
 3. The compressor according to claim 1, wherein the protrusion is tapered.
 4. The compressor according to claim 1, wherein the protrusion extends in the axial direction of the rotary shaft and has a constant cross-sectional shape and cross-sectional area in the axial direction of the rotary shaft.
 5. The compressor according to claim 1, wherein the distal end of the protrusion is semi-spherical.
 6. The compressor according to claim 1, wherein the protrusion is formed integrally with the rear housing member.
 7. The compressor according to claim 1, wherein the rear housing member includes an introduction port for introducing refrigerant into the suction chamber, and the introduction port extends in a direction intersecting the axial direction of the rotary shaft. 